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Experimental thermoreflectance measurements using femto-second laser irradiation (Hopkins et al 2011 J. Heat Transfer 133 044505) can be used to shed light on the electron-phonon coupling in metals through a selective excitation of electrons. In these experiments the energy transfer occurs at a time scale of pico-seconds which corresponds to the typical time scale of molecular dynamics (MD) simulations. However since the electron-phonon coupling is, generally, not taken into account in MD simulations, it is in principle not possible to model thermoreflectance as well as other properties related to electron-phonon coupling such as electric conductivity and thermal transport. Here we show that it is however possible to extend MD using a method proposed by Finnis, Agnew and Foreman (FAF) (Finnis et al 1991 Phys. Rev. B 44 567-74), originally implemented in order to account for electronic stopping power in particle irradiation. Although the FAF method was devoted to model high energy atomic displacements yielding local melt of the crystal, we have been able to reproduce pulsed-laser irradiation experiments at room temperature. Our computations were realized in both Au and Ni to exemplify the transferability of our results. The agreement between the calculations and the experimental results allowed us to discuss different theories for computing the amplitude of electron-phonon coupling and to select the more appropriate according to FAF. Our work paves the way to re-introduce the phenomenology of electric conductivity in MD simulations for metals., (© 2023 IOP Publishing Ltd.)

Using bulk micromachining, meander-shaped resistor elements consisting of 20 nm Cr and 200 nm Au were fabricated on 1 μm thick silicon nitride membranes, bridges, and cantilevers. The resistance change as a function of pressure depends strongly on the thermal resistance of the two metal lines connecting the heated resistor to the silicon bulk (cold junction) and on the thermal resistance of the silicon nitride. Relative resistance changes ranging from about 3% (small membrane) to 20% (bridge) per mW of input power were obtained when operating the devices in constant voltage mode. The pressure where maximum sensitivity of these gauges occurs depends on the distance 'd' between the periphery of the heated resistor element and the silicon cold junction. Devices with 'd' ranging from 50 μm to 1,200 μm were fabricated. Assuming that pressures can be reliably measured above the 10% and below the 90% points of the resistance versus pressure curve, the range of these devices is about two orders of magnitude. By integrating two devices, one with d = 65 μm and one with d = 1,200 μm on the same chip and connecting them in series, the range can be increased by about a factor of three. By fabricating the cantilever devices so that they curl upon release, it will be shown that these devices also exhibit larger range due to varying 'd'.